1. Field
Apparatuses and methods consistent with exemplary embodiments relate to an optically addressable spatial light modulator (OASLM) divided into a plurality of segments, and a holographic three-dimensional (3D) image display apparatus and method using the OASLM.
2. Description of the Related Art
Recently, in various fields such as the fields of entertainment, gaming advertising, medical imaging, education, military affairs, etc., a three-dimensional (3D) image display apparatus capable of representing an image in a realistic and effective way is desired. Consequently, various techniques for displaying a 3D image have been proposed, and various 3D image display apparatuses have already been commercialized. Currently commercialized 3D image display apparatuses use binocular parallax between a viewer's eyes, in which a left-eye view image and a right-eye view image, which have different points of view, are provided to the left eye and the right eye, respectively, allowing a viewer to perceive a 3D effect. Examples of the 3D image display apparatus include a glasses-type 3D image display apparatus which requires the use of special glasses and a non-glasses-type 3D image display apparatus which requires no glasses.
However, in the case of a stereoscopy type device using binocular parallax, a viewer may feel much eye fatigue and a change of a viewpoint due to a viewer's movement cannot be addressed because only two viewpoints of the left-eye view image and the right-eye view image are provided. Therefore, there are limitations to the ability to provide a natural stereoscopic effect. To display a stereoscopic image naturally by remedying this limitation, a holographic 3D image display technique has been studied.
A holographic 3D image display apparatus uses a principle that once a reference beam is irradiated onto a hologram having recorded thereon an interference pattern obtained by interference between a laser beam that is reflected from an original object and a reference beam, then the reference beam is diffracted and an image of the original object is reproduced. A currently commercialized holographic 3D image display apparatus provides a computer-generated hologram (CGH), rather than a hologram obtained by directly exposing the original object to light, as an electric signal to a spatial light modulator. The spatial light modulator diffracts the reference beam according to the input CGH signal, thus generating a 3D image.
In such a holographic apparatus, to allow a reproduced 3D image to have a sufficient resolution and viewing angle (that is, a large space bandwidth product), the performance of the spatial light modulator is important. For example, a spatial light modulator having about 1010 pixels in an area of about 100 cm2 is used. A generally used electrically addressable spatial light modulator (EASLM) is configured such that a drive circuit and an interconnection are disposed for each pixel. Consequently, there is a limitation in terms of reduction of the pixel size, such that the foregoing resolution requirement is difficult to meet. Thus, a holographic 3D image display apparatus using an optically addressable spatial light modulator (OASLM) has been proposed. The OASLM includes a photosensitive layer disposed on an incident plane of a write beam such that only pixels in a region in which the write beam is incident may be selectively turned on. The OASLM does not need a separate drive circuit or interconnection, and thus may satisfy the foregoing resolution requirement.
To generate a high-resolution CGH necessary for reproduction of a high-resolution 3D image, a large amount of computation is required. Therefore, to reduce the amount of computation required for CGH generation, various CGH generation methods and optimization methods have been suggested. One of them is an active tiling scheme of dividing the OASLM into a plurality of small tiles, generating a CGH for a relatively-low-resolution image corresponding to each tile, and sequentially providing the generated CGHs to the respective tiles.